Air-refrigerating machine



Sept. 15, 1925 5 1,553,546

' l. LUNDGAARD AIR REFRIGERATING MACHINE 6 667%( l WBYMW 1 sept. 15, 1925 1,553,546

|. I UNDGAARD AIR -REFRIGERATING MACHINE Filled May 22. 1922 4 sheets-sheet 2 Sept. 15, 1925 1,553,546

A l. LUNDGAARD AIR REFRIGERATING MACHINE Filed May 22. 1922 4 Sheets-Sheet 4 Q D x Q3 ibm K l Bf M MH H- ares ses' arresta.

Ivan LUNDGAARD, or Hen'rroan, comviicrrcur, .essie-Noa ro THE auroamrrc RE'- rnrennafrme coureur, or nan'rronn, connnc'rieur, .a conronarron or new Q'ERSEY.

' Application led MayV 22,

' izen of the Unite-d States, and a resident of Hartford, county of Hartford, State of Coni MR-REFRGERATING MACHNE.

1922. serial no. seaeoa.

constant pressure. Another object, is to produce a machine 1n whleh a given body of a1r will serve as a mediating fiuld| without additions or subtractions, the purpose 5 necticut, have invented certain new and usebeing to avoid the continual introduction ful improvements 1n A1r-Refr1gerat1ngMaof new air with its burden o-f moisture.

l0 dynamic cycle useful in connection with airor slightly lower.

' the connection.

chines, of which the following is a specification.

My invention relates 'to-a closed thermorefrigeration, and also to the construction. of an air refrigerating machiner operating according to that cycle. v

In a closed air refrigerating machine a body of confined airis alternately com-` pressed and expanded, the compression taking place in one chamber and' the expansion L in another chamber. The two .chambers are connected by a duct through which the me.- diating' air is transferred. A regenerator may be employed between the compression and expansion chambers to forma part of chamber is at a temperature below that of The air in the expansion Another object is to automatically establish the pressure during the cycle of operations so that the minimum pressure is atmospheric Other objects will appear from the detailed specication.

l attain these objects by the construction of my machine and aconsideration of the thermo-dynamic cycle will be given in connection with the accompanying drawings in whichl Figure 1 isa longitudinal vertical section taken through the centers off the two cylinders of my improved mach-ine.

Figure 2 is a vertical section taken on line 2--2 of Figure l with the actuating mechanism in elevation.

Figure 3v is a sectional detail view of one form of compensating connection between 25 the body it is desired to refrigerate and the the crank case and compression chamber.

air in the compression chamber is at a tem- Lrature above ythat of the atmosphere or other bodv into which heat abstracted by refl frigeration is to be discharged.

ln'my U. S. Patent No. 1,240,862, I have described an air refrigerating machine having a single cylinder equipped with a compression piston and a shifter piston for 'transferring the mediating air back and forth between the compression chamber and the expansion chamber through heat exchangers and a regenerator. The pistons are actuated by mechanism located in the crank case.

My present invention constitutes an im- .provement in the machine described in U. S.

Patent No. 1,240,862 and has for one of its 1 objects 'the utilization/of a thermo-dynamic cycle that will combine a"'relatively high average pressurewith a relatively low maX- imum pressure. This and other advantages I bring about by adopting a. cycle inlwhich the transfer of the mediating fluid from the compression to the expansion cylinder and the reverse is' effected atsubstantially the mediating air Figure 8 is a dia ram illustrating the .i

relative movements o the/compression piston and shifter pistonl during onje cycle.

. Referring more particularly to the drawings, Figuresl and 2 show the construction of an air refrigerating machine, according to my invention, having two cylinders, each with its owin body of mediating air, but it willfbe understood that any number of lcylinders may be employed. A base l has attached to it a crank-case2 by means of the bolts 3. Two-cylindrical extensions tare ,provided on the upper part of the 'crankcase 2. l Concentric with and fitted to the upper surfaces 'of members 4 are heat exchangers 5. Regenerators 6, also concentric with members 4, are fitted to upper surfaces of heat exchangers 5. Cylinder heads 7 are in turn applied above regenerators 6 and heat exchangers 8 are mounted thereon. Cylinderhead covers 9 are fitted above and central with cylinder heads 7 Gaskets may be used 4between the various parts to insure tight joints and the parts are held in place by the clamping action of bars 10,

`channel 11, compression members 12, bolts 13, and nutsy 14, by means of which the proper tension can be secured. Compress:y

` sion members 12 are of heat insulating material to prevent loss of heat from head covers. 9. f Liners 15 are inserted in the upper parts of cylindrical port-ions 4 of the crank case and liners 16 are inserted within heat exchangers 5. The cylinder walls are, therefore,` seen to consist of extension 4 of the crank case, liners 15 and 16, regenerators 6,v

heat exchangers 8.and cylinder heads 7. At the upper end of liners 15 annular ports 17 ',le'ad to the heat exchangers 5 and at the top of heat exchangers 8, annular ports 18 connect with the cylinders at their upper ends.

The movements of the pistons will be described in connection with one cylinder, but it will be understood that the movements of .the pistons vin the other cylinder are similarly performed. ompressi'on piston 25 is actuated by a pair of links 26 pivoted v at one `end, one on eachside ofv theaXis lof the piston. lLinks 26'are pivoted at their other ends on the two walking beams 27, which.

rock about pin 28. Motion is imparted to walking beams 27 by `connectingrods 29, the large ends of which work on crank pins 30 of crank shaft 31. A pulley 32 serves to `drive crank shaft 31. Shifter piston 40 comprises`a cylindrical shell 41 of heat-insulatuing material attached to a bottom plate 42.

` to keep roller 52 on the surface of the cam A piston 'rod 43, secured to plate 42 by nuts 44, extends along the axis of the cylinder through a bushing 45 in compression vpistonA 25, through the crank case 2 and into a guide bearing 46, which is secured tothe bottom .of the crank-case by nut 47. A

.spring seat 48 is attached to piston rod 43 by pin 49 and the lower ends of two links 50 are' pivoted on pin 4 9. The upper ends of links 50 are pivoted at one end of cam lever 5.1, which rocks about pin 28. At the other end of lever 51, a'roller 52' is mounted to rotate on pin 53 in contact with cam 54, which forms part rof .crank shaft 31. A compression spring 55, acting between spring seat 48 and a 4depression in the crank case, serves and also to actuate shifter piston` 4Q in the cylinder wall. vwith chamber 63, from the lower portion of up direction. Cam 54 causes the downward movement of piston 4() and controls its upward movement.

' Compression piston 25 is shown in its lowest-position and it will be observed that a passage 60 in the wall of piston 25 extends from the top of the piston to a point about half-way between the top and bottom, Where it registers with vaport 61 in the A pipe 62 connects port 61 tion of rotation' of the crank shaft as indi-' cated by the arrow. Inthe position shown, compression piston 25 is atl its lowest position and shifter piston 40 is at its highest position. The space between the two pistons will be designated the compressionv chamber and the space above the shifter piston 'the expansion chamber. Port 61 in Ythe cylinder wall registers with'passa'gevtiO in piston 25 and the compression chamber '1s in communicationr .with the crank case. Therefore, the pressures in the cdmp'ression chamber and crank c ase will be equal. As the crank shaft isrotated, piston 25 will L move upward, thereby closing port 61, while piston 40 will remain stationary. This acl tion results in compressing the mediating air in the compression chamber and some of the air will flow t-hrough annular port 17 .into heat exchanger 5, regenerator 6, 4heat -exchanger 8 and the expansion chamber. A

further rotation yof the-crank shaft causes a continued upward movement of piston 25 and a downward movement of piston 40. By these combined motions 'of the pistons,

the transfer of the mediating fluid from the compression to the expansion chamber `at substantially constant pressure is effected. It will be seen that the shifter piston is not held stationary unt-il the compression is completed, as hasbeen the case-in -previousmathe mediating fluid before the compression piston has nished its stroke. The' compressed air Hows through .heat exchanger 5 over leaves 19, which absorb/ heat due to the compression and .transfer it to leaves 20 from which it is removed by a cooling fluid circulating overl them. From heat exchanger 5 the compressed air passes throughregenerator 6 and heat exchanger 8 into the expansion chamber through ports 18. In heat exchanger 8, heat is absorbed by leaves llO chines of this type, but commences to shift circulates over themby means of pipes 22 l and 23. The heat absorbed is transferred to and the only opening from the atmosphere s leaves 211 by conduction and is. given up by the leaves to the mediating air. Still further rotation of crankshaft 3l results in a downward movement of piston'25 and an eq'ual downward movement of piston 40 resulting in an expansion of the mediating luid. The air is now entirely 4in the eXpansion chamber, with the exceptionof that contained in the heat exchangers and regcnerator, and has been expanded which hasy lowered Yits temperature. Further rotation of crank shaft 31 causes further downward motion of compression piston 25 and upward motion of vshifter pist-on 40. The expanded air is thereby transferred back through the heat exchangersand regenerator to ther compression chamber whichis accomplished at substantially constant pressure due to the combined motions of the two pistons.r This completes one cycle. The

vexact relative motion of the two pistons will tends to collect in the cold end in theform of frost, which ultimately clogs the air pas-- sages andr renders the machine inoperative.

To prevent 'any moisture entering thefmachine, l construct the crankcase and other parts so that all joints are completely tiglitV to the interior parts of the machine is the clearance around the crank shaft. To insure against air leaking either into or out of the machine, I provide an oil sealed stuffing box for thecrank shaft.

with suitableipacking, are provided `between solid bearing 76 and ball-bearing 77,"around crank-shaft 31 (Figure 2). Between the two bodies lof packing, a ring, 78 slidably mounted on shaft 31, forms a pocket to contain oil. "Ring 78 has recessesturned in its outer and inner surfaces, the recesses being in communication .by means of radially drilled holes. Gland 79 in connection with bolts 80, serves to compress the packing in spaces 75. An oil cup 81 acts-as a reservoir to hold a supply of oil for maintaining the pocket within ring 7 8 filled, through passage 82. This oil alsolubricates shaft 31. By the use of packing on both sides of ring 78, I keep the consumption of oil down to Spaces 75, filled 'an extremely low amount, and the leakage of air to a negligible amount. lt is to be noted that, with the construc- *tion a's described,` a ndefinite body. of air is contained within the machine, both as to mass and identity. When the machine isv not in operation, the pressure withinJ the compression chamber, expansion chamber and cranlr case will bethe same, since leakage by the pistons will'equalize the pres- 75 sure. l' prefer to have the pressure substantially that of the'atmos'ph'erewhen the ma` chine is idle, although a higher or lower pressure may bel-used since there is no communication to the atmosphere. When the,8G machine is started up the pressure of the mediating air will alternately increase and decrease as the cycle of operations proceeds and the mediating air will be transferred back and forth through the heat'eX/chan-gers S5 4 and regenerator between the compression and expansion chambers.` Since the latter. are always in communication with each other, the pressure in all parts of the mediating air is .always the same.

Assuming thatthere is no compensating connection from the4 space containing the mediating air to the crank case (as by passage/GO in piston 25, port 61, chamber 63 and pipe 64), it is apparent that after a few 95 revolutions of the machine, the 'average pres sure of the mediating air will equal that of' the crank c'ase, due to mleakage past the piston '25. This average Ipressure will be substantially lthatlof the atmosphere, if that pres- W0* sure .existed before starting up.' For exa1n ple, in` machines/'I have constructed, l' have found that if`\the greatest difference of pressure inthe mediating air during the cycle was ten pounds perL square inch, it varied from lfive pounds below atmosphere Ato iveA pounds above atmosphere. .l y

My compensating`- connection is provided to increase the average pressure of the mediating air. l/Vith piston 25 in its lowest position, the air is in the expanded condition and consequently at ornear the lowest pressure. Therefore, if at this instant'l conneet the comp-resison chamber to the' crank case, the pressures will equalize by the flow 'of-air through pipe 64, chamber 63, passage 62, port 61, and passage 60. At all other times during the cyc1e, port 61 is closed by piston 25 and no air can flow'through the compensating connection. By this means,

Vair'that leads past theh piston into the crank case, during periods'of highA pressure in the mediating air, is returned to the mediating air each cycle atithe time of low pressure. I have found that, by the use of 'my compensating' connection, the average pressure of i the mediating air may be increased from atmospheric pressure to live pounds per square inch above-atmopheric, while still maintaining ten pounds lfference between maximum lto provide for the increased average pressure. Due to the size of the crank case, this eifectis, however, very slight, but is suflicient to insure that any leakage occurring along crank shaft 31 will be of oil into the crank case instead of air out. of it. Y

-In a two cylinder machine, in whichone f piston is moving oppositely to the other, 'as

illust-rated in F vigure l," the total volume of air in the crank case is practically constant, so that there is` no change of pressure due i to piston movement, but merely a movement of the air Afrom one side 4of the crank case to the other, as the down.

In Figures vtto 7, I illustrate dia-grammatically the variations in pressure and volume of the mediating airvthroughout one cycle, as I prefer to' CarryitOu-t. One cycle corresponds to one revolution of the crank shaft and I have divided the operation into four periods, A, B, C and D, each representing one-quarter revolution. In Figure 4, the vertical distance from line X, X at any point, to the solid lines bounding theshaded area, gives'the distance of the compression piston from its upper position, and the distance to the dottedlines, gives the distancev of the shifter piston from its upper position, hence the vertical distance from line X, X to the solid and dotted lines respectively, ,repiresent-s the volume at any instant in the compression and expansion chambers. During period A, the vmediating air is being transferred from the compression chamber to the expansion chamber., `During period B, the mediating air is being expanded in the vexpansion chamber. During period C, the air is being transferred back to the compression chamber and during period D, it is being compressed.

In Figure 5, the total volume of the mediating air is shown and the vertical distance below line X', Xrepresents the total volume at any point during the cycle. In Figure 6, the manner in which the pressure varies is shown and the vertical distance above line X, X, represents the pressure at any stant pressure P. Due to a lowering of itsl temperature by the cooling heat exchanger and Jthe regenerator, the' a1r decreases 1n pistons move up and.

volume from V,l to V2.' During period B, the air is expanded in the expansion chamber from pressure P to p audits volume increases Afrom V2 to V3, its temperature decreasing. During period C, the air is transferred back to the compression ychamber at the lowV pressure p. Due tothe action of1` the refrigerating heat exchanger and the regenerator the volume of the air is increased from V3 to V4 and its temperature 75 rises. During period D, the. air is compressed in the compression chamber from volumev V4 and low pressure'pto volume V,l and high pressure P, its temperature increasing. n

My cycle, therefore, comprises expansion and compression and a heat change in the medium under isobaric conditions. I havey found many advantages in constructing my machine to operate according to the above described cycle, which is accomplished by properly coordinating the movements of the compression and shifter pistons, as will be described in connection with Figure 8. One of .the chief advantages `over that of machines utilizing a cycle in which the transfer of the mediating air is carried out '-under conditions of constant volume, is the decrease in dierence of pressure required between P and 10 for a given refrigerating capacity. This means a greater thermo-dynamic eiliciency and a more ,even torque curve, and consequently less starting torqueand less fly wheel weight. i The parts may also be lighter as they are not requiredto withstand'as great pressures. Furthermore, there is less leaka e past the compression piston and aroun the piston rod. of the shifter piston and also a lower mechanical loss.

The usual indicator diagram is given1 in Figure 7, and it shows the work done inlcompressing the mediating air and the work returned by the expansion. The area P, V2,

Vw p is the work of expansion and P,'V1,

V4, p is the work of compression. The net work per cycle is given by they area V2, V1, V4, V3, and must be supplied by the driving, motor or other driving mechanism.

In order that my machine may operate according to the above described cycle, it is '115 necessary that `the compression and shifter pistons have the proper relative motion. It is seen that the motion of the compressionI piston is imparted to it by crank pin 30, cnnecting rod 29 and walking beam 27 through links 26 (Figure l). yBy plotting with rectangular coordinates, the motion ofthe compression piston with respect to time, as rep.- y resented by the rotation of the crank shaft, We have curve I) of Figure 8, in which the ordinates are `piston travel and the abscissae are degrees of rotation of the crank shaft. Line A, A represents the bottom ofl the stroke and line B,.B the top of the stroke ofI the compression piston. Line C, C repre` 1.30

sents the upper limit of travel of the shifte'r piston and curve E gives the shifter pistonv travel plotted with respect to the rotation of the crank shaft. Therefore, the'vertical distance at any point fromfline C, C to curve D represents the total volume of the mediating air at that point (neglecting the clearance volume) and the vertical distance between curves E and D represents the volume in the compression chamber, while the vertical distance from line C, C to curve E represents the volume in the expansion chamber.

The motion ofthe shifter piston is controlled by cam 54 acting through roller 52, l5 lever 5l, links 50 and rod 43. It will be readily understood that the motion of the .shifter piston according to 'curve E is attained by properly profiling cam 54 so that,

as the compression piston performs the montion corresponding 'to the sine curve D, the shifter piston remains stationary at .its top position during the period from 0 to 120, moves downward to meet the compression piston during the period from 120 to' 180,

follows the downward motion of the compression piston during the 'period from 180 to 27 0 and returns tofits top positionduring the period from 270 to 360, which completes one cycle. 30 Y x) stant pressure to an expansion cylinder by a shifter piston while continuing'the motion of the compression piston. l

2. The method of operatingrefrigerating e machinery which comprises compressing a mediating fluid .in a compression cylinder, transferring the mediating uid from the compression cylinder at substantially constant pressure to an expansion cylinder by a shifter piston while continuing the motion of the compression' piston, expanding the mediating fluid in the expansion cylin' der and transferring the mediating fluid at substantially constant pressure fromthe expansion cylinder to the compression cylinder by a shifter piston While continuing the motion of the expansion piston. i f L 3. The method of operating refrigerating machinery which comprises lcompressing a mediatingfluid by means of a piston in a.

compression cylinder, transferring the mediating fluid from the compression cylinder through a regenerator at substantially con-v stant pressure to an expansion cylinder by a' shifter piston while continuing the mo- 5 tion of the compression piston.y

@tour of the cams and their angular relation Although the embodiments as described. present the novel features of my invent-ion` 4. 'lhe'method of operating refrigerat'ing machinery which comprises compressing a mediating fluid by means o'f. a piston in a. compression cylinder, transferring the mediating fluid from thecompression cylinder through aregenerator at substantially constant pressure t0 an expansion cylinder by a shifter piston while continuing the motion of the compression piston, expanding the mediating fluid in theexpansion cylinder and transferring the mediating fluid at substantially constant pressure from the expansion cylinder to the compression cylinder by a shifter piston while continuing of the expansion piston.

5. In a refrigerating machine of the closed i cycle type using a gaseous mediating fluid,

the combina-tion of a chamber having a hot end and a cold end, a piston for compressing Vthe mediating fluid in said chamber, a shifter the motion for transferring the mediating fluidl from one end of thechamber tothe other, a crank shaft having cranks connected to the piston -and cams connected to the shifter, the conto the cranks beingsuch that the mediating fluid, by the combined action of the shifter and piston, is transferred from one end of the chamber to the other at substantially uniform pressure. c

6. In a refrigerating machine of the closed cycle type using va gaseous mediating fluid, the combination of a chamber having a hot end and a cold end, a piston for compressing the mediatingfluid in said chamber, ashft- ,er for transferring the mediating fluid from one end of the chamber tothe other, a crank shaft having cranks connected to the piston and cams connected to the shifter, a crank case supporting the chamber and containing the crank shaft and articulating mechanism, means for sealing ,the journal bearings of the crank shaft in the crank case and a passage from said crank case. to the chamber for connecting the crank case with the' chamber when the piston is in its position of minimum compression. f i

7. n a refrigerating machine of the closed cycle type using a gaseous mediating Huid, the combination of a chamber having a hot end and a cold end, a piston -for compressing the mediating fluid insawidchamber, aj shifter for transferring the mediating fluid from one 4end of the chamber tothe other, a driving shaftarticulated with the piston and the shifter so that the mediating 4fluid by the combined action of the piston and shifter. is transferred from one end of the ingthe mediating luidf in said. chamber, a."

shifterfor transferring the mediating Huid' case and a passage from said crank case to from one end of the chamber to the other, the chamber for connecting the crank case 10 a crank shaft having cranks lconnected `to With the chamberfwhenfthe piston isin its the piston and cams connected to the shifter, position of minimum.y compression, and' a crank case supporting the chamber and means interposed inthe connecting passage containing the crank shaft and articulating for abstracting moisture from the mediating mechanism, means for sealing Ythe journal fluid.

hearings of the crank shaft in the crank p IVR LUNDGAARD. i 

